SANGER. — CHRONIC ARSENICAL POISONING. 159 



added. After 30 minutes, the lamp is moved back to the second 

 heating place, the rest of the solution added, and the heat maintained 

 for 80 to 60 minutes longer. Of the two mirrors thus obtained, one 

 has been used to confirm the presence of arsenic by solution in sodic 

 hypochlorite, or, when possible, by the odor on heating, while the 

 second has been retained for reference. In case the amount of arsenic 

 is too small to divide, the whole may be collected in one mirror. 



I have found the careful destruction of the organic matter to be 

 necessary, as a comparatively small quantity of organic matter in the 

 reduction flask is of decided hindrance to the reduction of the arsenic 

 and deposition of the mirror. That this is the case seems to be the 

 general opinion, although Chittenden and Donaldson* state that their 

 results are not affected by the presence of organic matter. They were 

 able to recover from 50 c. c. urine, introduced into the flask directly 

 with a few drops of olive oil to prevent frothing, the original amount 

 of arsenic added, besides getting a distinct mirror from 0.01 mgr. It 

 would, however, be impossible to work with the concentrated solution 

 of a large quantity of urine without destroying the organic matter 

 partially, and I have taken the precaution to destroy it thoroughly, 

 particularly as the use of the method as a quantitative one depends on 

 the uniformity of deposit of the arsenic mirror, and this cannot be 

 assured in the presence of organic matter. 



The cases in which the analytical work fell to me are as follows : — 

 Case 1. In the autumn of 1883, Mr. A. and wife took a house in 

 Cambridge, of which four rooms, parlor, dining-room, study, and bed- 

 room had been recently papered. In the spring of 1885 the halls of 

 the house were covered, and either in 1883 or 1885 the other rooms. 

 These papers contained the following amounts of arsenic calculated 

 as arsenious oxide. 



* Amer. Chetn. Journ., II. No. 4. 



